Power converters have been used in power supplies for voltage and power conversions. High efficiency power converters are needed in many applications to reduce the power losses and the heat generated, shrink the size and cut the cost of the power supplies and the cooling equipment. Power converters with wider voltage regulation range generally have lower power efficiencies compared to converters with narrower voltage regulation range and unregulated converters, and vice versa, given that other aspects and conditions of the converters are comparable. Voltage regulation capability and power conversion efficiency are often two conflicting things for high efficiency power conversions.
A forward converter is a direct current (DC)-to-DC converter that uses a transformer to provide an output voltage different from the input voltage. The ratio of the output voltage to the input voltage depends on the ratio of windings around a core (typically a ferro-magnetic core). A flyback converter makes use of a diode or transistor on the output side of the transformer to prevent power from being drawn from the converter while current is flowing on the input side. A capacitor is also placed in parallel with the load, maintaining a supply voltage while current on the output side is blocked by the diode. When power is disconnected from the primary side, current flows through the diode, recharging the capacitor.
Resonant converters include a tank circuit (comprising at least one inductor and at least one capacitor) that actively participates in determining input-to-output power flow. Operation at the resonant frequency reduces impedance, increasing power conversion efficiency.